Shear foil for a dry shaver

Abstract

A shear foil for a dry shaver has a flexible sheet material body a central portion of which is provided with holes of a diameter between substantially 0.3 and 0.7 millimeters for the passage of beard stubble, and peripheral portions of which serve as mounting portions and are provided with holes of a diameter smaller than those in the central portion but not less than substantially 0.02 millimeters. The holes in the respective portions are separated by sheet material strips whose dimensions are so selected that the bending resistance of the shear foil body is substantially uniform throughout and that the portions of the body can withstand the maximum expected tensile and pressure forces.

We claim: 
     
       1. A shear foil for a dry shaver, comprising a flexible sheet material body having a central portion provided with holes of a diameter between substantially 0.3 and 0.7 mm for passage of beard stubble therethrough, and perforate peripheral shear-foil mounting portions being lateral edges and provided from the central portion up to said edges with a continuous field of holes of a diameter smaller than at least some of those in said central portion but not less than substantially 0.02 mm, the holes in the respective portions being separated by sheet material strips and the bending resistance of said sheet-material body being substantially uniform throughout. 
     
     
       2. A shear foil as defined in claim 1, wherein the ratio of the width of said strips to the diameter of said holes in said peripheral portions is about 3:1 so that said shear foil has a substantially uniform bending resistance throughout its length and width. 
     
     
       3. A shear foil as defined in claim 1, wherein the ratio of width of said strips to the diameter of said holes in said central portion is constant and the ratio of width of said strips to the diameter of said holes in said peripheral portion is also constant. 
     
     
       4. A shear foil as defined in claim 1, wherein said central portion has transitional regions which merge into said peripheral portions and in which said holes of said central portion have a diameter which is the smaller the closer they are to said peripheral portions. 
     
     
       5. A shear foil as defined in claim 1, wherein said central portion has transitional regions which merge with said peripheral portions and in which the center-to-center spacing of said holes of said central portion is the larger the closer such holes are to said peripheral portion. 
     
     
       6. A shear foil as defined in claim 1, wherein said central portion has transitional regions which merge into said peripheral portions and in which said holes of said central portion have a uniform diameter but the center-to-center spacing between adjacent holes is greater than in the remainder of said central portion. 
     
     
       7. A shear foil as defined in claim 1, wherein said central portion has transitional regions which merge into said peripheral portions and in which said holes of said central portion have a uniform diameter but the center-to-center spacing between adjacent holes is smaller than in the remainder of said central portion. 
     
     
       8. A shear foil as defined in claim 1, wherein said central portion has transitional regions which merge into said peripheral portions and in which said holes of said central portion have a uniform center-to-center spacing but their diameter decreases in direction towards the respective peripheral portion, the holes in said peripheral portion having the same diameter as the holes which are located in said transitional regions immediately adjacent the respective peripheral portions. 
     
     
       9. A shear foil as defined in claim 1, wherein said central portion has transitional regions which merge with said peripheral portions and in which said holes of said central portion have a uniform center-to-center spacing but their diameter decreases in direction towards the respective peripheral portion, and wherein the holes of said peripheral portions also have uniform center-to-center spacing and their diameter decreases in direction outwardly, away from the respective transitional region. 
     
     
       10. A shear foil as defined in claim 1, said sheet material body being a peripheral margin and being provided with cut-outs other than said holes; and further comprising metallic reinforcing layers on said peripheral margin and on portions of said sheet material body which bound said cut-outs. 
     
     
       11. A shear foil as defined in claim 10, wherein the dimensions of said reinforcing layers correspond to the dimensions of said sheet material strips of the portion whereon said layers are provided.